1. Field of the Invention
The present invention relates to a method of electronically controlling the operation of an internal combustion engine mounted, for example, in an automobile or the like, and to an electronic control apparatus for executing the method.
2. Description of the Related Art
A conventional widely applied method of controlling the operation of an internal combustion engine mounted on an automobile or the like consists of detecting various data that represent operation conditions of the internal combustion engine such as the number of revolutions, the amount of intake air, determining by calculation the amount of fuel to be fed to the internal combustion engine, ignition timing and the like by using an electronic control device such as a microcomputer, and controlling the fuel injection valve in accordance with the thus determined amount of fuel to be fed and controlling ignition timing of the ignition device. In such a method of controlling operation of the internal combustion engine, however, the data representative of the amount of intake air used for calculating the amount of fuel to be fed is data from the previous cycle. At the time of, for example, rapid acceleration, therefore, the amount of air actually sucked in the cylinder is different from the amount of intake air used for calculating the amount of fuel to be fed, and thereby the torque produced by the internal combustion engine undergoes a change which causes vibration and thus gives the driver an uncomfortable ride. This is due to the fact that, in general, a relatively small torque is produced when the air-fuel (A/F) ratio in the cylinders is lean and a large torque is produced when the A/F ratio is rich.
In order to accomplish optimum control of fuel supply during such a transient period, therefore, a fuel injection control device has been proposed as in, for example, Japanese Patent Laid-Open No. 261625/1987 in which the amount of fuel to be fed is determined by estimating the forementioned data immediately after the fuel injection valve is opened based upon the data inputted just before the fuel injection valve is opened.
In the fuel injection control apparatus of the above-mentioned prior art, the data just after the fuel injection valve is opened is estimated from the data just before the fuel injection valve is opened. In practice, however, this estimation is so difficult that there develops a difference from the amount of air actually sucked, making it difficult to exercise optimum A/F control. For example, it is very difficult to estimate the amount of intake air, particularly under the idling operation condition in which the number of engine revolutions tends to vary up and down a small amount. Under such a condition, the internal combustion engine tends to produce excessively large or small torque resulting in an increase in vibration.
In view of the above-mentioned problem inherent in the prior art, the object of the present invention is to provide a method of controlling operation of an internal combustion engine which does not cause variation in the torque even when the A/F ratio deviates from the optimum value in each of the cylinders of the internal combustion engine and which, therefore, is capable of smoothly producing torque with suppression of vibration, and to provide an electronic control apparatus therefor.